We shall continue to study factors and mechanisms that determine specificity of catecholamines on biochemical mechanisms in heart, smooth and skeletal muscle and adipose tissue. The biochemical mechanisms are those involving cyclic nucleotides and protein phosphorylation in the control of glycogen metabolism and contractile properties. We are returning to our earlier interests in the interaction of lipolytic and lipogenic hormones with the effects of nutrition, particularly acute fasting followed by refeeding with diets varying in carbohydrate and lipid composition. Here we intend to study the integration of covalent modification of enzymes, allosteric mechanisms and the physical association of the enzymes of glycogen metabolism in the depletion and resynthesis of the glycogen and adipose tissue. Another important question is whether the specificity of hormone-neurotransmitter action is conditioned by the consequent activation of a specific pool of cyclic AMP-dependent protein kinase in proximity to specific substrates for protein phosphorylation. Much of this work will continue on heart but begin on adipose tissue as well.